This invention relates to dipotassium chloroimidodisulfate, and is particularly directed to a substantially stable crystalline dipotassium N-chloroimidodisulfate.
Detergent compositions containing a water soluble detergent surfactant, and generally a builder which is used to sequester calcium and magnesium ions and to improve detergency levels of soaps and synthetic detergents, are widely used in home and industrial laundries for cleaning fabrics. Such detergent compositions may also contain fillers, such as sodium sulfate, and minor amounts of optical brighteners, soil antiredeposition agents, perfumes and the like. Although such detergent compositions effectively remove soil from fabrics, such as polyester, polyester/cotton, cotton and the like, certain stains on the fabric caused by tea, grape juice, red wine and the like, are very difficult to remove from fabrics using conventional detergent formulations.
To remove stains caused by tea, grape juice, red wine and the like, it is a common laundry practice to add a bleach to aid in the removal of such stains from the fabric. The most common bleaches are the peroxide-type bleaches and the hypochlorite-type bleaches, such as sodium perborate and sodium hypochlorite, respectively. However, each of these bleaches suffer from certain disadvantages. The peroxide-type bleaches usually require an activator to be effective and particularly in cold or tepid water. On the other hand, the hypochlorite bleaches can effectively remove the stain but such stain removal is frequently accompanied by some damage to the dyed fabric. Furthermore, it is often desirable, if not necessary, to segregate white clothes from colored clothes to minimize the deleterious effect of normal use levels of hypochlorite bleaches on colored fabrics and to prevent the transfer of dye from colored fabrics to white fabrics.
Those skilled in the art of detergent formulations have long been interested in a material that is stronger than the peroxide-type bleaches and would act in cold or tepid water, but yet is not as strong as the hypochlorite-type bleaches that have a deleterious effect on dyes and fabrics, and yet have a desirable bleaching property. In a copending application Ser. No. 838,279 filed Sept. 30, 1977 now U.S. Pat. No. 4,148,742 issued Apr. 10, 1979, a process was disclosed for washing soiled fabrics comprising contacting the fabrics with an aqueous detergent composition which includes a surfactant, a halogen-containing bleach and a bleach damage mitigating amount of trisodium imidodisulfate, tripotassium imidodisulfate or mixtures thereof. The combination of the hypochlorite and the trialkali metal salt of imidodisulfate provided a chloroimide bleach which is intermediate in strength between the hypochlorite and the peroxides, i.e., the intermediate bleach is strong enough to remove stains from the soiled fabric but yet is not so strong as to unduly damage the dyes and the fabric.
Although satisfactory results are achieved by the compositions in the process set forth in the copending application, those skilled in the art of detergent formulation are interested in a material useful as a bleach, intermediate in strength between the peroxides and the hypochlorites that could be formulated directly into a dry detergent formulation. It has been found that the disodium chloroimidodisulfate, which is formed when trisodium imidodisulfate is reacted with hypochlorite, in situ, in the washing process according to the teachings of the copending application is not stable as a solid since it rapidly loses the available chlorine. Furthermore, the literature reports that potassium chloroimidodisulfate is unstable as a solid (see, for example, F. Raschig, "Potassium Chloroimidodisulfonate", Z. Anorg. Allgem., Chem., 147, pp. 1-4 (1925)). Now, according to the present invention, a dipotassium chloroimidodisulfate is provided which is substantially stable in dry air at room temperature and normal atmospheric pressure, which can be prepared as a solid, and which is intermediate in strength as a bleach between perborates and hypochlorites.